The invention relates to a process for the synchronization of a time division multiplex (t.d.m.) system having a plurality of data channels, with a multiplexer which makes available a total of m time slots per t.d.m. frame, and emits a multiplex signal; with a transmitting-end synchronizing bit generator which produces synchronizing bits which are transmitted in the frame of the multiplex signal from the transmitting-end to the receiving-end; with a receiving-end pulse generator for the production of a bit pulse train; with a receiving-end address generator for the operation of a demultiplexer; and with a receiving-end synchronizing discriminator which, with the aid of the synchronizing bits, produces a synchronizing signal for the operation of the address generator.
The same synchronization of t.d.m. systems is carried out, as is known, by transmitting, in each t.d.m. frame, a plurality of synchronizing bits which together form a synchronizing word. By receiving-end decoding of this synchronizing word, the position of the t.d.m. frame is recognized and a t.d.m. frame synchronization is facilitated. If the synchronizing words are formed only from a relatively small number of synchronizing bits, the probability of simulation of synchronizing features by data words is relatively great, so that frequently systems of this type are subject to interference. If, in contrast, the synchronizing words are formed from a plurality of individual synchronizing bits, the simulation of synchronizing features by data bits is low, although a relatively large proportion of the channel transmission capacity is needed for the transmission of the synchronizing information. Synchronizing words of this type, which consist of a plurality of synchronizing bits, also have the disadvantage that during the course of the synchronization monitoring, in the event of a breakdown in the synchronization, an alarm signal can only be produced with a relatively long delay.
The aim of the invention is to provide a process for frame synchronization which, in spite of insensitivity to simulation of synchronizing features, necessitates only a relatively low channel transmission capacity and which facilitates a rapid alarm triggering during the course of the synchronization monitoring in the event of a breakdown in the synchronization.